1. Field of the Invention
This invention relates in general to pressure transducers for sensing pressure within tubular members, and in particular to a method and apparatus for inductively sensing pressure within a subsea wellhead housing.
2. Description of the Prior Art
Prior Art pressure transducers have been used for monitoring fluid pressures within tubular members, such as subsea wellhead housings. Typically, pressure within tubular members have been monitored by coupling a prior art pressure transducer to a port passing into the interior of the tubular member. Another prior art means has been to secure resistive strain gauges to the exterior of tubular members for monitoring pressure therein.
For oil field applications, a need exists to periodically monitor the pressure in certain tubular members in well installations, both on land and at sea. For example, in one type of well, an outer wellhead housing will enclose an inner wellhead housing. The inner wellhead housing directly supports casing, tubing and the like which are subject to high pressure. The annulus surrounding the casing is normally not under any pressure. The annulus surrounding the casing communicates with a lower portion of the interior of the inner wellhead housing. In the event of leakage in this casing, the inner wellhead housing would be subject to pressure.
Checking the pressure in the inner wellhead housing would indicate whether or not any casing leakage has occurred. In the prior art, this is not done because installing a pressure sensor would require drilling a hole through the sidewall of the inner wellhead housing for receipt of one of the above-mentioned typical pressure transducers. However, because of the possibility of leakage, operators prefer to avoid drilling holes through the sidewall of wellhead housings. Further, because of the harsh and corrosive environments often encountered in petroleum well installations, prior art resistive strain gauges may not adequately perform over the service life of a wellhead housing.